Marine propeller steering system



Feb. 9, 1954 H. J. NICHOLS MARINE PROPELLER STEERING SYSTEM 5 Sheets-Sheet l Filed July 30, 1948 INVENTOR.

, May/0.45'

ATTORNEYS Feb. 9, 1954 H, 1 NICHOLS 2,668,514

MARINE` PROPELLER STEERING SYSTEM Filed July 30, 1948 5 sheets-Sheet 2 IN VEN TOR.

H. J. NICHOLS MARINE PROPELLER STEERING SYSTEM Feb. 9, 1954 3 Sheets-Sheet 3 Filed July 50, 1948 HARRYd NICHOLS ATTOR N EY Patented Feb. 9, 1954 UNITED STATES PATENT OFFICE 2,668,514 MARINE PROPELLER STEERING SYSTEM Harry J. Nichols, Point Pleasant, N. J. Application July 30, 1948, Serial No. 41,656

This application is a continuation-in-part application of my application Serial No. 433,991, led March 9, 1942.

' This invention relates to controllable and reversible pitch propeller systems for marine and naval vessels.

More particularly, it relates to mechanism for varying the pitch of the propeller blades while the propeller is stationary or in rotation under load, and a system for controlling the pitchvarying mechanism whereby the pitch can be varied manually or regulated automatically to adapt the propeller action to various operating conditions such as light or heavy loads, towing, maneuvering, stopping, backing, and constant speed operation or automatic rudderless steering by pitch regulation.

An electric master controller is provided for the remote control of the propeller pitch, as for example from the navigating bridge and other locations. Another feature of the invention is the provision of control means whereby the pitchvarying mechanism can be placed under the joint or optional control of a plurality of agencies such as an automatic speed governor, a helmsman, and an automatic pilot. Further control features are means for remotely indicating the pitch vof the propeller, automatic follow-up means whereby the pitch is automatically brought to a preselected angular position and stopped there, and automatic warning signal means. l

It is known of course that various types of variable-pitch and reversible-pitch marine propel- 1ers have been devised and used. These devices have met with considerable success in practice, but have been characterized by complicated construction, or by elaborate, costly, and heavy machinery, such as pressure pumps, hydraulic rams, and the like. It is a general object of the present invention to provide a controllable pitch marine propeller organization characterized by relative simplicity, reliability, durability, flexibility, high eiciency, and low cost.

Another object is to provide a practical pitchvarying mechanism whereby a relatively feeble control-torque is greatly amplified and utilized to produce a change of pitch. As a direct consequence, the amount of power required for control purposes, and the size, weight, and cost ofthe pitch-varying mechanism is greatly reduced, while the versatility and efciency of the apparatus as a whole is greatly increased.

A further object is to provide a pitch-varying mechanism of unlimited angular range, including reversing the pitch, which is capable of gradually 9 claims. (c1. 11s-35) changing the pitch in minute increments, yet also is capable of changing the pitch at a rapid rate at will. A further object is to provide pitch-varying mechanism which can be applied without extensive modication of the normal marine propeller and propeller shaft arrangements; Vwhich involves a minimum of change in the normal propeller design; which permits the actuating and control apparatus to be mounted convenientlyinside the vessel; which is readily installed and serviced; and in general meets the rigid requirements for marine use. Other objects will be in part obvious from the annexed drawings and in part hereinafter indicated in connection therewith by the following analysis of this invention. This invention accordingly consists in the features of construction, combination of parts, and in the unique relation of the members and in the relative proportioning and disposition thereof, all as more completely outlined herein. l To enable others skilled in the art fully to comprehend theunderlying features of this invention, that they may embody the same by the numerous modications in structure and relation contemplated by the invention, drawings depicting a preferred embodiment of the invention form a part of this disclosure, and in such drawings like characters of reference denote corresponding parts throughout the several views, in which- Fig. 1 is a side elevation in partial axial section of a marine variable pitch propeller and drive shaft therefor embodying certain features of the invention;

Fig. 2 is a cross-section of line 2 2 of Fig. 1;

Fig-3 is a cross-section on line 3 3 of Fig. l;

Fig. 4 lis a schematic diagram showing the elements of the pitch control system; Fig. 5 is a series of diagrams illustrating typical positions of the master controller dial;

Fig. 6 is an elementary diagram to illustrate the principles of rudderless steering; and

Fig. 7 is a schematic diagram illustrating the application of the invention to either or both of the propellers of a twin-screw installation.

General description Considering the invention as a whole, and referring to Fig. 1 generally, the compound epicyclic-gear torque-amplifier Ill is mounted bodily as a unit on the propeller shaft I2, preferably inside the vessel as for example at the coupling with a drive shaft I I. The entire pitch-changing mechanism rotates bodily with the shaft at shaft speed, the gears normally being at rest relative to each other. A radial spur-gear transmission assembly (see Fig. 2), mounted in a special nange-coupling, transmits pitch-changing torque from the torque-amplifier IG to a torsion shaft 24 mounted inside propeller shaft I2, and thence, via ring bevel gear 25 and individual blade gears 26, to the individual propeller blades 2l (of which onlyone is shown in Fig.k 1 in order to simplify the drawings), of the twin propellers PP and SP, as in Fig. 7.

By applying a directional control torque to the planetary wheel I5 of thetorqueanipliiier I0, as for example by a reversible motor M and a chain drive 44, the torsion shaft 2liis caused to turn gradually in one direction or the other, whereupon the pitch is increased `or decreased as the case may be. The torque-ampliiier gears are self-locking, that is the torque-amplifier gear train cannot be driven backwards by the blade reaction.

The entire gear mechanism is inherently statically and dynamically balanced, a plurality of balanced pinions being employed to distribute the load reactions and to secure good teeth action. The gear mechanism as a whole is exceptionally enicient and smooth running.

The characteristics of the pitch-changing mechanism 4,make the invention adaptable to any power, speed, or other probable propeller design requirement'. The construction is such that the blade can turn indenitely in either direction, hence the range of pitch-change is unlimited;

p The power required to cause a change of pitch varies over a considerablevrange, dependingon rate Vof change and operating conditions, but the external control-torque is always small compared to the augmented torque utilized for pitchchanging, say a few percent thereof. Consequently, the control motor is quite small compared 'to the driving equipment of other systems. Suitable remote controlapparatusis provided to regulate the vpitch to various operating conditions, including quick reversing 'and rudderless steering. The system as a whole, including the three primary control devices described, constitutes a true servo-system'.

The variable pitch propeller Referring .to the drawings more in detail, and particularlyto Fig. l in which a typical variable pitch propeller vconstruction suitableto the in vention is shown, the propeller shaft I2, mounted in bearings supported by the vessels Astructure (not shown), is provided with an, annular groove I2g adapted to receive a vsplit ring 32 and key ways, adapted to receive keys 33 (one being shown), by which means the propeller hub 34 is secured to shaft I2. A sleeve 3 I, also fitted with key ways, and recessedto receive ring 32, andadapted for attachment to hub 3Q by through bolts 35 (one being shown) also forms part of the hub assembly.

Propeller bladesZI (only one beingv shown) are rotatably mounted in hub 34 by any suitable means, Ysuch as anti-friction bearings 35 and 3l', in such manner that they can `be rotated axially without limit in either direction.V Each blade is provided with a bevel gear 2 6 mounted ast'on the shank thereof by suitable means such as bolt 28. A ring bevel gear 25, slidably but non-rotatably mountedon torsion Vshaft 24 andA uiournalled in'a bearing 29 mounted in'hub'34,isheldtightly' in mesh with the blade gears by a thrust 'bearingA 3 3 mounted on cover disc 39. The ihub `3"4-'is made in two transverse sections to facilitate assembly of the blades and their bearings therein, and is fitted with a hub cap 34e in the usual manner. The hub assembly is water tight and is self-lubricated by contained grease in well known manner.

The pitch-changing mechanism Referring now' to Figsl to 3; tliepitelilchanging mechanism comprises generally the torqueampliier I0, the transmission gear assembly 23, the torsion shaft 24, and the bevel gears 25 and 26 in the propeller hub. The drive shaft II is p'r'oi'fided with a flange IIa spaced from a ila-nge I2a on the propeller shaft I2 by a ring I9, Fig. 2, the assembly being tightly held together by through bolts I8 to form a combined shaft, coupling and gear housing. The torque-amplifier I9 comprises planetary or epieyclic differential gearing consisting of stationary internal gears I3 mounted ixedly on propeller shaft I2, driver planetary carrier I5 (herein called the planetary carrier), mounted rotatably and concentrically on shaft I2 and carrying compound planetary pinions III-IS, and driven internal gears I'I rotatably mountedon shaft I2. lGear I3 is in mesh with pinions I4 and gear Il is in mesh with pinions I5. Gear I'I is also provided with an extension rim passing over Aflange I2a and formed with internal teeth It which mesh with pinions 2E of the transmission gear assembly. The pinions 2I are mounted in recesses {Sa (Fig. 2), formed in ring I9 andare journalled in flanges Ila and I2a and mesh with sun gear 22 mounted iixedly on torsion shaft 24, the latter being rotatably mounted concentrically within the hollow of shaft I2 by anti-friction bearings 23 and extending therethrough to the propeller assembly. Flange IIa is provided with external gear 4I and gear II is provided with an equal external gear 42, these gears meshing with equal pinions 5I and 52 driving the rotors of rotary transmitters TI and T2 respectively. Planetary carrier I5 is equipped with external sprocket teeth 45 adapted to cooperate with drive chain 44, driven by electric motor M by means of sprocket 40, as shown clearly in Fig. 3.

In operation, the whole gear system normally rotates bodily with the shaft, the planet pinion teeth locking the internal gears of the differential gearing in stationary relation, the chain drive and motor M turning over idly. If it is desired to change the pitch, electric current is applied directionally to motor M to cause the chain drive to drive planetary carrier I5 in one direction or the other. For example, assuming that itis desired to decrease the pitch, reverse current is applied to energize the Vmotor M to cause planetary carrier I5 to rotate counter-clockwise relative to the propeller shaft, assumed to be rotating clockwise, the effect beingwto slow downplanetary carrier I5. Thereupon, planet pinions Iii-IB begin to roll in the adjacent internal gears 23-II producing a slow counter-clockwise creep of gear II with-.respect to vstationary gear I3. Internal gear I'It thereupon drives pinions 2| which in turn drive sun gear 22, whereby torque is transmitted via torsion shaft 2li4 to decrease Athe pitch of the blades. Naturally, the pitch change continues so long as planetarycarrier I5 has relative rotation and at a rate proportional to such relative rotation. It Yshould here b eunoted that applying braking action to cause backwards relative rotation of -planetary carrier I 5-, as for example by' connecting themotor so as to cause regenerative braking as explained hereafter, the planetaryaction would be as explained above, vand the pitch decreased accordingly.

To increase the pitch, motor M is energized to cause wheel I5 to speed up relative to its normal rotation. Thereupon, pinions I 4-IB roll in the adjacent internalv gears I 3-I 'I to produce a withrotation creep of gear Il which is transmitted through the transmission as before described, but.

in reverse sense, to increase the pitch of the blades. As before, the pitch-change continues so long as there is relative rotation of planetary carrier I5 and at a rate proportional thereto. From the above, it is evident that the rate of pitch change can be varied over a wide range by regulating the duration of motor current and/or by varying the speed of motor M according to well-known practice. For small changes of pitch, motor M can be energized only momentarily and due to inertia of the motor and planetary drive, the relative change of speed would be small, and the pitch change micrometric. changes of pitch and particularly for quick reversing during emergencies, full current can be appliedto motor-M for a substantial period, accelerating the motor to full speed in either direction to change the pitch at the maximum rate. M f

Pitch control system Y K Referring now to Fig. 4 which illustrates by means of a schematic diagram one application of the pitch control system of the invention, TI and T2 represent the identical rotary electrical transmitters of Fig. l; These rotarytransmitters, similar in construction to small S-phase induction alternators and preferably provided withr permanent magnetic eIds'andadapted to generate S-phase alternating current whose frequency is proportional to speed of the rotating member of rotor. Rotary transmitters of this type being well known in the electricalart in connection with synchro-tie systems, 'detailed description of their construction here is unnecessary.

' The transmitters are driven by pinions 5I andv 52 meshing with spur gears 4I and 42 operatively associated with ange IIa of drive'shaft II` and with gear I'I, respectively. These gears are cut to the same number of teeth and to the samek pitch diameter. Likewise, pinions 5I and'52 of transmitters TI and T2 are duplicates. Therefore, so long as gear I1 and ange IIa rotate together, transmitters TI and T2 generate 3phase alternating currents of the same frequency, but not necessarily in phase. These currents are distributed by 3-wire mains, as indicated, to as many rotary electrical receivers as desired, as for example R and RI. These receivers are similar in construction to small, wound-rotor, B-phase induction motors, and being well known inthe electrical art in connection with synchro-tie systems, detailed description here is unnecessary. lt should be noted, however, that the current from one transmitter is connected to thefstator windings of the receivers, while the current from the other transmitter is connectedto the rotor windings of the receivers. The connections are inconsistent order, following well knownprinciples, so that the rotors of R and RI assume an angular relation to their respective stators which represents the diiference in phase between the currents produced by TI and T2. It is to be understood that the rate of rotation of the rotors of TI and T2Uis immaterial, so far as receivers R But for large and RIY are concerned, but that relative angular displacement of the rotors of TI- and T2 produce corresponding angular displacements of the rotors of both R and RI with relation to their respective stators, thereby indicating angular relations between-drive shaft II vand the pitchchanging gear I'I.

. In ultimate analysis, the pointers of the indicating and controller devices reflect by angular position the degree of pitch change of the propeller vblades relative to an arbitrary reference niark on the propeller hub. These indicating and controller devices can be provided in duplicate and located at convenient remote points, such as the bridge, pilot house, emergency station, etc. providing a controlsystem of unusual flexibility, versatility, adaptability, and convenience. The indicator device I, actuated by the shaft of receiver RI and forming a part of that unit if desired, consists essentially of a rotary pointer PI and stationary concentric dial DI with arcuate scale graduated to indicate propeller pitch-angle relative to normal position, that is degrees ne (F) or coarse (C) with respect to an arbitrary origin. It is in eifect a remote electrical pitchangle indicator, and for brevity is hereafter referred to as the pitch indicator l. Y

The indicating controller device, referred to as the controller K, consists essentially of a rotary pointer P operated by the shaft 54 of receiver R, a stationary concentric dial D with arcuate scale graduated to indicate the relative pitch-angle of the propeller; and a rotatable commutator as shown in Fig. 5 comprising conducting segments SI, S2, S3, mounted on an insulated setting ring 55 rotatable concentrically with the dial. Segments SI and S2 are positioned so as to be electrically contacted by contactor or brush By shown as integral with the dial pointer. Another brush B3 is mounted diametrically opposite P. One side of an electric current source is connected to these brushes. Segments SI and S2 are electrically connected to relays LI and L2, respectively, via the main control circuits. Between segments SI and S2 is a short neutral gap bisected by index contacts to form switch XI and preferably with a slow-release device on the magnet core as indicated. The contacts of XI when actuated carry current from the mains to the control motor M. Let it be assumed that relay LI functions to increase the pitch as previously described, hence LI may be termed the coarse relay. Relay L2, also preferably of slow-release type, is likewise provided with double break-make contacts to form switch X2 which when closed carries reversed current to motor M to cause the pitch to be decreased, hence L2 may be termed the ne relay. Furthermore, should relay L2 be energized for a prolonged period, the pitch. will eventually be reversed from normal, reversing the propeller thrust. It should be noted that the contacts of relays LI and L2 are so interconnected that in the eventv both relays operate, the power circuit is acosa-1r opened. Hence', iti's` impossible for thetwo relays to produce a short Ycircuit by simultaneous action.k

As an emergency safety' m'easure for marmeinstallations', a safety switch X5 is provided which, when thrown to the alterna-te position, short circuits motor M, the effect of which? is to apply re'-` gen'erative braking thereto, which causes Wheel t5' to slow down and thereby decrease .the pitch.Y Thus in' the event controlwere lost under c'irl0 cumstances requiring emergency reversing; the` propeller cou-ld nevertheless'V be reversed by ace. tuating switch XS. For marine installations, the' emergency regenerative braking could be arranged so that slxoul'cl'` t-he speed increase unduly l5' in 'ne' pitch, the blades would betbrought back quickly to a safe, coarse pitch, and operated ata suitable iixed pitch for the' duration of the emergency. Other emergency measures', such' asbo'cst-l ing? the motor voltage to increase the rate of pitch 20 changesare'readily applied, due tothe versatility ofi' the pitchcontrolY system.

M anual' operation The normal manual opera-tion of the pitch-com 25 trol system is as follows: Assuming that the pitch` is to be increased from normal setting asV at A inrFig. 5; that is madecoarser, the rotatable setting ring 55 of controller K is turned cloclnviseasL atl b in- Fig. 5'4 until the index mark 5t stands: at' 30 say -i-i.- Thereby, theauxiliary circuit isbrolren:4 asbrush B3 leaves segment S3V and current is applied to segment Si by brush l2y (symbolized by pointer p), which'energizes relay LI which hyact-uationofi the blades cswitch XI appliesVV current 35 to motor M to cause'clocliwise rotation-ofy Wheel |.5=as previously described: As gear il is' turnedvvv differentially clockwise inresponse' to the rotation-I oi carrier'lthe pitch is increased and transmitter Ti gains phase proportionallyl over tran's- 40 mitter T2; so that-the' phase change Alzaetvv'eer'ithese` transmitters energizes-receiver Rto'tuin pointer P oi controller K in the clockwise direction. Like: wise, pointer P t of indicator I' is actuated fthrough thelsystem which Lfurmtions as 'ai follow-up means* 45' therefor tofshow the pitch change"` Asl the pitch increases and" pointer P approaches the index mark. 56; brushB-loses Contact Withsegmentsl cutting. off the'currentirom relay Li. Whencu-i' rent'. is thus-cut off', after a'prief delay relay' Biff 50 dropsout, whereupon contacts XI transferto'vl i" movecurr'entrom motor M, thereby terminating" thepitch-change (The main purpose of' theU brief1 delaye inthe` drop-out of relaysll': aindllfv is-ftofensure that the brushes de'niteiy clear the' 55 segments, avoiding theY possibility oi" destruct eburningoith'eccntact members.) Asthe pointer Preturns'to neutral position vbetween 'segnieritsSlf' and S2, hruShBSreturns toinormalipositio'r-*or segment'S3-J 60 In" similar manner, to decrease' the'fpitcl,'-tlf setting ring `55=is`turned`the desired' aiiouritcue ter-clockivi'se-inthe" dial a'sA at cfinf Fig- 51V Thereupommelayrmis energized from segment-FST actuating-contacts X2 to `put revise'current-i nmotor JlViiwhi-chv `drives wheel i 5" in th'e'reverse"d1-` l rection.- This :results: in easing" or reversing-*the pitch as: previously: described.v Asl' th'ef pitch changev progresses, Y the pointers Pand Pl areI turned counter-clockwise accordingly? hyf the r'lv 70" regardless' of the prior change. .It is evident that merely vlcy manipulation of controller K the pro-- peller pitch can be varied effectively to maneuver a vessel in docking; as well as for stopping and backing.

Thus it is lto loe noted that merely by moving the'setting ring 5.5 to the selected .pitch indica-a tion; the proper devices are selectively energized and actuated* to cause kthe propeller pitch( to' be changed. a corresponding amount inf the proper direction', whereupon the pitch changing operai# tion' is automatically term'inateds. This con# stitutes kthe pitch responsive automatic follow-'upl and cut-off feature; as essential to a' true servo``l`v System'.

Constant speed?r operation' l lieferung-again', to Fig. 4, the primary control elementforconstant speed operation is' pref-V QFafblY a centrifugal governor SGpof iiyWeig-ht type ,drerlbr the propeller engine at a' speed proportional-,to the enginespeed. The principles and construction of flyweight governors, being, Well known, extensive description here is deemed unnecessaryj In this caseLthe governor .actuates a contactoror brush' B4 connectedin the auxiliary control circuit and adapted to make, electrical contact alternately with segment S6' or segment Sl. Asuitable speed adjusting mechanism is provided to adjust the tension of the governor speed-spring, so'r thatat thedelsired speedv level brush B4 rests" iii thf nemal' gap between the segments S6 and' ST as shown..

TheV operation to" establish' and; maintain aj constant speed` is as' `follows: Assniing thai-theI engine 'throttle has been set at' the approiii'riiate' speed', the governorl SGi's'set' at thefdesiredspeefd. and the governor slides brush BITy up or; down', accordingto' the eiisting" speed;y s'suiiing that the speed is to@ 10W, VmusaBtwur,resi-f on see? ment Sl' Whichbeingv electrically connecteduithf the fine relay L2 will' energizefthe ,s'anie and cause the' pitch to beLdeorea'sed asf before dei sented. neeteasingv the einen naties tu, gine to'ruii fa'ste'i" at' the" same'throttle'settirigl hence the rengine speed increases andjprush` BI' royes` `toivardtheneiltral g f' Aft substantially calibrateuxspeed .th'ev'arious factor-s eddie inno; balance with brush Bdf in thereutif'aLgap andf the' propeller operating at r,iix'efd pitch.1 .But slioiild'tlfie speed change`tlie`g'verrir reipro'l dates brushBtoselecti-vely energizefre'lay Ll'` or' mil as `required to'. regulate theibiadritch to' maintain. constantA engine speed. p

It is to. be noted', 4hovveveijthat should the sich'.penetrerend www@ B3 will" as@aratrs-egmar sa; @parte the auxiliar. @str-Q1 .iruit se that the: cur-reni supply: to, brushc B4 win benut oir, ternana-tine the control" oigovernorl SG; AItis alsol tofl be noted that fthe reactonpr the pitch Y' changeonv the governor' causes the latter toterminate the control Y' Cycle. Thusf thesystern under the primary'controi oi the lgovernor constitutes-,aservo-r system. Y

Automtefruddm'lcss steering Thief facility aridi preoisionfvvitli which" the' propeller pitch? car he controlledby thisinve'n tion-7 nia'lee pessime' andi practical autolnatic ruddrlsi* steerffefgi jwih-Slyji weer by" pitch"regniY tionfofjtliepropllers; Forthatpure' f maarssen-#a Ac'ccrdinglyzthe' rfid weer; r requis'itwotpropellers can' 'bef'clearly explained by describing the actuation of a single propeller of a twin-screw installation by the means-of the invention. Y'

. The principle of automatic rudderless steering can be readily understood by referring to Fig. 6 which shows in elementary manner the normal forces acting on a twin-screw Vessel due to the action of its propellers, the port propellerbeing indicated by PP and the starboard propeller by P.V The essential fact is that in driving the vessel ahead each propeller accelerates a stream or jet of water astern, producing a forward thrust on the propeller which pushes the ship ahead. So long as the jets are in equal momentum, the

y thrusts are balanced, and the vessel tendsl to move ahead .in a straight line. But if the jets become unequal, the unbalanced thrusts produce a turning movement of the vessel 'around itsI center of gravity C. G. which diverts the course into a curve, thus producing a steering eifect. Unequal jets .can be produced by unequal speeds and/or unequal pitches of the two propellers. But for present purposes, and preferably in practice, the speeds of the propellers are assumed to be equal, and steering to be effected by regulating the pitch of either or both propellers slightly, herein termed pitch regulation, according to steering conditions. However, it is to be understood that the speeds and pitches of the propellers can be varied greatly and the pitches reversed, for producing radical changes of course or for maneuvring.

For purposes of automatic steering by pitch control, termed automatic rudderless steering, the primary regulation element of the automatic pilot control arrangement is a special steering compass indicated as SC in the diagram of Fig. 4. This compass is preferably equipped with a rotatable setting ring 51 carrying electrical contacts whereby control .currents are transmitted to the electrical pitch control apparatus. The needle CN of the steering compass of course always tends to point to true north (N), while the settable compass ring l turns around the needle as the vessel turns. The needle CN is equipped with a contact brush B2, symbolized by the arrowhead, adapted to make electrical contact with two short segments S4 and S5 mounted on setting ring 51 and separated by a neutral gap. Needle CN is normally connected to the auxiliary control circuit leading from segment S3 of controller K, while segments S4 and S5 connect with the windings of relays LI and L2 respectively. Ring 51 is set so that the needle CN centers in the neutral gap when the vessel is. I

on the desired course. Hence, as the Vessel turns away from the course to which the ring 57 is set, one or the other of the relays is energized by the control circuits leading from the segments.

Illustrative of the operation of the pitch control apparatus for automatic rudderless steering, let it be assumed that the vessel is steady on its set course heading true north, that the speeds and the pitches of the twin propellers have been equalized, and that the needle CN is steady in the neutral gap between segments S4 and S5. The automatic pilot apparatus is therefore inactive. Should the vessel veer to the right, segment S4 would be brought into contact with brush B2, thereby applying energizing current to relay Li which applies operating current to motor M to increase the pitch of the blades of the starboard propeller. The momentary effect of this increase of pitch will be to cause the starboard propeller SP in Fig. 6 to propel astronger l0 jet rearwardly, and hence the starboard thrust on the vessel will be increased, tending to tur-n the vessel to the left, that is, back to its original course. Should over-correction occur, the compass needle CN will contact segment L to ener- The automatic warning signal During` the automatic steering process (and during constant speed operation), the pointer P of the master controller K will perform short excursions to either side of the zero ,0, but brush B3 will normally retainY contact with segment S3, enabling SC to regulate the pitch. But should the pitch variations tend to accumulate in one direction or the other, or a major departure from the set course occur, brush B3 will lose contact with segment S3, breaking the auxiliary control circuit and SC will therefore lose control. In that event, a special warning signal circuit will be energized from either segment S4 or S5, as the case may be, and the warning signal WS will be actuated; It will be noted that the warning signal WS, preferably a relatively high impedance device such as a telephone bell, is connected in series with a circuit from the (-1-) power main to the auxiliary control circuit from segment S3. Thus when the auxiliary control circuit is broken at S3, but the main control circuit is closed at S4 or S5, current will iiow from power through WS Via S4 and Ll, or S5 and L2, to power. If desired, it can be so arranged that the operating current for WS is less than the required operating current for Ll and L2 so that the latter are not affected by the warning signal current.

In this connection, it should be noted that in any case where the vessel is not brought back to the set course by a small change of pitch, the warning signal WS will give notice of the fact. Thus attendants will be apprised of the manual circumstances and proper corrective measures can be taken, as for example by promptly returning the vessel to the set course by manipulation of the master controller. This constitutes the automatic off-course warning signal feature.

During constant speed operation under the control of governor SG, should the circuit be broken at segments S3 by a marked change of pitch, but closed at segment 6 or segment 1, the warning signal WS will be energized to give warning of loss of governor control. This constitutes the automatic off-speed warning signal feature.

Cut-out switches X4 and X5 are provided to put the speed governor SG and the steering coinpass SC out of action if desired. However, it is deemed preferable to have master controller K ready to function at all times, so that the propeller pitch is automatically maintained at or near the desired value. Thus, for example, should the steering compass SC tend to produce an abnormal degree of pitch change, master control K will automatically take charge to limit .the pitch change, thus providing aV safeguard canes-,tia

1 l .againstudld steering. .Hence:no.cuteout;;.switch vvis shown for .the master controller, .althoughisuch fa switch could obviously be-provided kif desired.

' Twin' screw control Referring now to-Fig. '7 which illustrates the application ofthe pitch .control vsystempf the -invention to either or vboth of thetwo control-A Y.lable reversible .pitch propellers of a twin screw installation, the schematic diagram thereshown utilizedV tocontrol either .oneor both of' thepro- A.pellers of a twin screwinstallation'for purposes of. automatic rudderless steering.

Referring to Fig. 7 in detail, double pole switches Xp and Xs are provided for putting the single steering compass SC alternatively in'control of either one or both of the propeller'pitch changing systems for purposes of automatc'rud- 'derless steering. The circuits associated with switch Xp connect SC operatively'to relays Ll and L2, which in turn control port 'pitch changing motor Mp; andthe circuits associated with `switclrXs .connect SC' operatively with identical relaysLl and L2' which in turn control'starboard pitch changing'motor Ms. Theserelays function as described in connection with the. dian ,gram shown in' Figyl, and all theadditional elements of apparatus are mere duplicates of those shown Yin'Iig. 4, hence detailed description of the apparatus is not required.

"In ...automatic rudderless .steering of a 'twin screwvessel, the steering effects ofthe two'propellers are relatively reversed, that is, an increase of thrust of onepropeller produces substantially lthe same steering effect as a decrease of thrust of the other propeller and vice versa. Hence it should be noted that in Fig. 7.the steering com- ,pass' SC is connected tothe control relays L of thesport controls inversely with respect tothe control relays L ofthe starboard controls. I'he control. arrangements illustrated provide three optional .conditions for automatic .rudderless steering. If only switch Xs is closed, the starboard propeller is controlled by steering compass SC to eiect automatic' rudder-less steering as ldescribed in connection with' Fig.. 4. If onlyswitch `Xp is closed, theport propeller iscontrolledby steering compass ASC toleffect antomaticrudderless-steering;V control relaysLl andLZ, however1 I being .actuated inversely. If .both switches Xs .and'Sp .are closed, both propellers. are :controlled ...as before by compass SC to effect-automatic rudvder-lessesteering. In the last instance, however, more-steeringacticnwould as :a rule'be-exercised in bringing the vessel back to the V-preset compass course. .'I-Ience.V in practice, .the choice ...between the three optionalv control set-ups rwill .eas-1a rule be governed by the sea and weather "conditions, and the tendency of the vessel to'be .set oir itscourse in one directiony or the other.

It willbe obviousto those skilled in the 'art that-substantial increased average vessel speed and-savings in propulsion'power, aswell as 'sav- -ving wear-and-tear on'thesteeringfengine, will VKresult :from the .v application of vautomatic rudf-derless fisteerin'g. This follows :.mainly r from f the i12 @fact that :a f'r-.udder i produces :considerable idrag when 'acti-ng toesteert fa vessel, :or` when'faccertain rudder angle is required to hold the vesselonits course, -wlrlleI controlling l thepitch Vfor 'steering does not intrQduOeany additional'drag.

-It-will'be evident to those skilledfin therart thatlthe' pitchcontrol apparatus described providesexceptional flexibility and versatility of control.' and that various control functionsi can :be obtained by combining the control elementsx-in .various-Ways. Therefore it isunnecessary to lde scri-be the vvarious switching 'arrangements rsby which these'combinations can be eiected.

Wit-houtv further:analysis` the foregoing fwlll: `so

^ .f fully. revealgthe gist of this invention that'L-ot-hers Lean, by applying current knowledge, readily :adapt itfor vari-ous'applications` without omitting. certain.v features f that, f. from the standpoint of 'the .prior art, fairly constitute .essential 1 characteristics ofl the..generic:or specific aspects' of .the dnvention,z vand therefore such vadaptations :should and are intended to be comprehended'withinthe .meaning and range of equivalencyof the following claims.

I claim: 1. In a propulsion system' for-atwinfscrew'vessel, combination; means fordriving saidvessel f including a; pair :of controllable: propellers, ,individual means forA varying .the pitch offeachof said propellers includingranzelectric. motorlfdrivingly. connected to saidzpitchi varyingtnieansfand automatic electrical control :means 4operatively connected Vin control frelation .to one 'of isaid "motors for control-ling `'said one 'motor' for'purposes of steering said'- vessele'automatically" comprising a compassresponsive to achangeof course of said vessel havingy .a :fixedV direction' element and electrical contactingfmeans operatively-con powermeans connected to "drivef each" propeller,

and individual power `means J operatively vconnected tofvary Ythe pitch of each-of said .propellers the combination. comprising 'pitch control'means .operatively connected to actuate independently each Aof saidfindividual` 4power means, andi automaticpilot steering .means `operatively associated 'with eithenor bothfof saidipitchfcontrol means forpurposesofsteering said craft automatically on .f a .Y set -1-course, f said 1 automatic pilot steering means .including :compass means for detecting :deviationsfsaid'craft from aA set course, course :setting'means operatively associated with said vcompassimeans and' means operable to connect v`'said "compass means and said course setting means so as to actuate either or both of said pitch control means tocorrect said deviations, whereby the relative pitch'of said propellers can bev auto matically regulated to maintain said craft on a fset'course.

.3.v In 'a'..propulsiori system for a twin screw "craft of thekind including motive means for drivingtsaid craft. Va.' pair of controllable pitch .marinepropellers driven thereby, 'power means `individual .l-to each propeller Yoperatively con- -75 '.'necte'dto' varyA the.'pitch-"thereof, andpitch control means operatively connected to actuate independently each of said individual power means; automatic pilot steering means adapted to actuate either or both of said pitch control means for purposes of steering said craft automatically on a set course, including compass means for detect ing deviations of said craft from a set course, course setting means operatively associated with said compass means, and means for connecting said compass means and said course setting means to actuate either or both of said pitch control means so as to correct said deviations, whereby the pitch of either or both of said propellers can be automatically regulated to maintain said craft on a set course.

4. In a propulsion system for driving a vessel including a pair f controllable pitch propellers having substantially parallel propeller shafts located on opposite sides of the center line of said vessel and each having blades rotatable about their own axes; the combination of power means individual to each propeller operatively connected to rotate axially the blades thereof; individual pitch control means operatively connected to each of said power means for controlling independently each of said power means and thereby to vary the pitch of the blades of the associated propeller; and automatic pilot apparatus operatively associated with said pitch control means, including compass means for indicating the course of said vessel and responsive to a change of course thereof, settable means operatively associated with said compass means for presetting a desired course of said vessel,

and means jointly actuated by said compass means and said settable means for automatically regulating either or both of said power means and thus the relative pitch of said propellers, whereby the vessel can be automatically steered on a preset course by pitch regulation.

5. In a propulsion system for a vessel including a pair of controllable pitch propellers located on opposite sides of the center line of said vessel anddndividual pitch changing mechanisms operatively connected to each of said propellers for changing the pitch thereof, the combination of individual pitch control means operatively connected to each of said mechanisms thereby to vary independently the pitch of said propellers, and automatic pilot apparatus operatively associated in supervisory control relationship to said pitch control means for regulating either or both of said pitch control means and thus the relative pitch of said propellers as required to automatically steer said vessel on a preset course solely by pitch regulation.

6. In a propulsion system for a twin screw vessel including controllable pitch twin propellers and individual mechanisms for changing the pitch of each of said propellers, in combination, individual pitch control means operatively connected to each of said individual mechanisms for varying independently the pitch of said propellers, and automatic pilot apparatus operatively associated in supervisory control relationship to said pitch control means and being selectively connectable to said individual pitch control means singly or jointly, thereby to regulate the relative pitch of said propellers so as to steer said vessel on a set course.

7. In a propulsion system for a twin screw vessel including a pair of controllable pitch propellers for driving said vessel, the combination of individual power means having a driving connection to each propeller for changing the pitch ill thereof, individual pitch indicating and controller means including a master pitch controller operatively connected to each of said individual power means and adapted to vary independently the pitch of each propeller and follow-up pitch indicating means for continuously indicating the pitch of each associated propeller during maneuvering of said vessel, and auxiliary automatic pilot apparatus operatively associated with said pitch control means, and including means for presetting a selected vessel course and means for detecting deviations from said course, for regulating said individual pitch control means singly or jointly so as to counteract such deviations, thereby to steer said vessel on the selected course solely by pitch regulation.

8. In a propulsion system for a twin screw vessel including a pair of controllable pitch propellers and individual mechanism for changing the pitch thereof, the combination comprising pitch control means operatively connected to each said mechanism including for use during maneuvering of said vessel, a pitch setting means and a juxtaposed follow-up pitch-change indicating and pitch-change cut-off element for setting and indicating the pitch of each said propeller individually and for cutting off said pitchchanging means upon the pitch of said propeller having been changed in accordance with the setting of the pitch-setting means, and settable automatic pilot apparatus operatively associated in supervisory control relationship to said pitch control means for controlling selectively said pitch control means singly or jointly thereby to regulate the relative pitch of said propellers as required to steer said vessel on a preset course solely by pitch regulation.

9. 1n a propulsion system for a twin screw vessel including a pair of controllable pitch propellers, individual mechanism operatively connected to each of said propellers for changing the pitch thereof, individual power means having a driving connection to each said pitch changing mechanisms, individual pitch control means including a settable master pitch controller and an associated follow-up pitch indicating means operatively connected to each of said power means for varying and indicating the pitch of each propeller independently during maneuvering of said vessel, settable automatic pilot apparatus adapted to modify the action of said individual pitch control means as required to steer said vessel on a preset course, and means for connecting said automatic pilot apparatus with either or both of said master pitch controllers as required to maintain the vessel on said preset course.

HARRY J. NICHOLS.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 980,156 Hertzberg et al. Dec. 2'7, 1910 1,065,142 Key June 17, 1913 2,185,074 Chance Dec. 26, 1939 2,279,301 Colley et al Apr. 14, 1942 2,307,039 Hammond Jan. 5, 1943 2,307,040 Hammond Jan. 5, 1943 2,319,435 Rassweiler et al. May 18, 1943 2,340,174 Chance Jan. 25, 1944 FOREIGN PATENTS Number Country Date 221,483 Great Britain July 23, 1924 

